资源环境科技发展态势分析平台

The vertical temperature profiles of the equatorial Indian Ocean between the latitudes 5 degrees S and 5 degrees N in years of El Nino and monsoon drought have been studied using quality controlled ocean temperature (EN4) data set of the UK Met Office Hadley Centre and Simple Ocean Data Assimilation (SODA) reanalysis data. The temperature anomalies in the equatorial Indian Ocean were studied in three composites: (a) years of El Nino with no drought monsoon (composite A), (b) years of El Nino associated with drought monsoon (composite B) and (c) years of monsoon drought without El Nino (composite C). In composite A, a prominent subsurface dipole (SSD) in temperature is seen between depths of 60 and 120m during the months September-November. It is not present in composite B. SSD is associated with surface wind anomalies, easterly in the equatorial central Indian Ocean and southeasterly in the equatorial eastern Indian Ocean. Drought monsoons have strong westerly surface wind anomalies in the equatorial central Indian Ocean, which reduces the strength of the equatorial easterly wind anomaly in composite B. In composite C, a negative SSD developed due to the strong anomalous westerly wind over the equatorial Indian Ocean associated with monsoon drought and the absence of El Nino induced equatorial easterly winds.